Burglar alarm



Dec. 29, 1931. J. H. FITZPATRICK 1,838,813

BURGLAR ALARM Filed April 7; 192'? 1'0 L jf if J Illllhllglllll l nin l l3 E3 Patented Dec. 29, 1931 JOHN HENRY FITZPATRICK, OF CHESTNUT MOUND, TENNESSEE BURGLAR ALARM Application filed April 7, 1927. Serial No. 181,773.

;, ments permit the switches to close and sound an alarm.

An object is to provide a novel self-locking relay which will maintain an alarm or other electric circuit closed until the locking latch is is manually released.

The invention consists in novel features of construction, formation, combination and ar rangement of parts to be hereinafter more fully described, claimed and illustrated in the accompanying drawings, in which Figure 1 is a diagrammatic view of the switch controlled circuit of a burglar alarm system,

Fig. 2 is a perspective view of one of the flexible cord controlled switches of such a circuit, and

Fig. 3 is a detail perspective view of my novel relay controlling the alarm circuit and showing the locking latch thereof dotted in locked position.

In a burglar alarm system such as is shown in 1, there may be provided switches of the type illustrated in Fig. 2 and including a bracket 7 having mounted thereon a block 8 of insulation. Pivotally mounted upon the block is a switch arm 8 which is normally positioned between spaced contacts 10 carried by the frame 11. The arm 9 closes a circuit when it moves upwardly or downwardly.

To the switch arm is secured one end of a frangible cord 12 which may be trained zig zag or in any other manner over the door, window or other closure to be protected. The bracket 7 is provided, at the lower end, with i l ear 13 to which is secured a helical spring 14, one end of which is secured to the switch arm 9, the spring serving to hold the arm balanced between the contacts 10 and also holding the cord. 12 under tension.

Leading from the switch arm 9 is the conductor 15, see Fig.1, which connects with a switch contact 16 carried by the door. Leading from a companion contact 17 on the door is a conductor 18 which connects the contacts 10. The contacts 16 and 17 cooperate with switch blades 18 and 19 fixed to the wall and so located that, when the door is closed, the contacts 16 and 17 will engage the blades.

A. signal 21 is placed in a suitable location and is in circuit with the armature of my improved relay 22 and with a battery 23 throu h conductors 24 and 25. The winding of t e relay is in circuit with the switch blades 18' and 19 and with a battery 26 through conductors 27 and28.

My improved relay includes spaced switch contacts 31 which are connected to the alarm circuit wires 24 and 25. The coil of the relay 22 is disposed in upright position between the contacts. The armature 30 of the relay is substantially U-shaped in contour and is piv oted to swing on a horizontal pivot below the coil, as may be seen by referring to Fig. 3, and straddles the coil. The legs of the armature engage the contacts 31 onopposite sides of the coil when the armature is moved by energizing of the coil. 7 y

In order to automatically clamp the armature against the coil 22 and against the contacts 31 for maintaining the alarm circuit closed after energizing of the coil,I dispose a stationary right angular bracket 32 below the armature with the upright leg of the bracket terminating in close proximity to the armature. A. straight latch or lever 29 is pivoted near one end to said upright leg of the bracket, near the top of the leg. The lever normally projects horizontally from the leg and bears, with its short end, against the underneath face of the armature. The long end of the lever forms a weightwhich is adapted to gravitate and swing the lever on its pivot, pendulum-like, to vertical position underneath the armature, as shown by dotted lines in Fig. 3, with the extreme upper end of the lever wedged by the pivot against the underneath face of thearmature to positively clamp the armature to the coil and to the contacts until the lever is manually released.

It will be understood that all circuit wires 9 and parts effectingthe operation of the device will be secreted in such manner that access cannot be had thereto, thus preventing a burglar from disconnecting circuits.

In operation, should a burglar succeed in using a torch to penetrate a bank vault door equipped with the invention, the flame of the torch will sever the cord 12. Thereupon, the spring 14 will pull the switch arm 9 downwardly into engagement with the lower contact 10 thus energizing the relay and closing the circuit to the signal 21. lVhen the relay is energized, the armature 30 will shift, thus permitting the latch or lever 29 to gravitate m to the dotted line position shown in Fig. 3, thereby holding the armature in a position to cause the alarm to sound until the lever is manually released.

Should the vault door be dynamited, the explosion will naturally warp the door, and it is for this reason that a pair of vertically disposed contacts 10 are illustrated in connec tion with the application of the invention, since the warping of the door is apt to so distort the same that the switch arm 9 will swing upwardly, which being the case, it will contact with the upper contact 10 and close the circuit, thus sounding the alarm, as above described.

. The signal 21 is illustrated as abell but, of

course, it will be understood that a siren may be used, if desired. The signal-may be placed in some inaccessible location upon the building or it may be located in a police station, as rlesired.

Having thus described the invention, 1 claim:

An electric switch apparatus comprising spaced switch comacts, a relay having up- .:;5 right coil disposed between the contacts, a U- shaped armature pivoted to swing on a horizontal pivot below the coil and straddling the coil, the legs of the armature engaging "the contacts on opposite sides of the coil when the armature is moved by energization of the coil, and means for automatically clamping the armature against the coil and against the contacts for sustaining an electric circuit after energization of the coil compris- 'ing a stationary right angular bracket below the armature having an upright leg terminating in close proximity to the armature, and a straight lever pivoted near one end on said upright leg near the top of theleg, said lever normally projecting horizontally from said leg and bearing with its short end against *the underneath face oft-he armature, the long end of the lever forming a weight adapted togravitate and swing the lever on its pivot pendulum-like to vertical position underneath the armature with its extreme upper end wedged by the pivot against the underneath face of the armature for clamping the armature to the coil and to the contacts until the lever is manually released.

In testimony whereof I afiix my signature.

JOHN HENRY FITZPATRI'CK. [L. s] 

